Suppose you have placed windows into a straight Wall (at the given distances from either end of the Wall), then later curve the Wall (as in the picture below).
The appearing Openings’ Position dialog box allows you to choose how to handle the openings’ new position in the curved Wall:
Keep distance: This option will ensure that the openings’ distance from the nearest Wall end remains unchanged. (Openings are measured from their center point.)
Note: The Wall segment that you click to curve will be the segment that is stretched.
Keep proportion: This option will keep constant the position of the openings relative to the Wall length.